Greenwood, who was part of England's Rugby World Cup winning side in 2003, is leading the expedition to climb the world's tallest free-standing mountain for the charity Borne, which raises funds for research into premature births.

The cause is close to Greenwood's heart as he and wife Caroline lost their son Freddie 45 minutes after his birth in 2002 - he is also patron of the Child Bereavement Trust.

"Some of our toughest rugby guys do not get to the top of Kilimanjaro. Being physically able and fit and having a resting heart rate of 55, being able to do a three-hour marathon makes no difference on Kilimanjaro."

Will Greenwood

Greenwood endured some tough training sessions during his playing career, but few of those came at the 3,000 metre altitude he will have to deal with next month.

He has been going through some punishing sessions at The Altitude Centre in London but knows it is going to take a massive team effort from all involved in the walk if they are to achieve their aim of completing the Rongai route and raising £250,000 for Borne.

Borne, which was set up by Professor Mark Johnson, is working in the UK and Africa to change the long term health prospects of hundreds of thousands of children and their families through research and education.

Physical challenge

Greenwood said: "Some of our toughest rugby guys do not get to the top of Kilimanjaro. Being physically able and fit and having a resting heart rate of 55, being able to do a three-hour marathon makes no difference on Kilimanjaro.

"It's going to be a team effort. We're going to stick together and we're going to do it. We're all going to have our own individual reasons for doing it and we'll all carry our own different personal memories and motivations to get to the top.

"Clearly Freddie will be close with us but for me there are certain people you meet in life who you owe everything to. Forget about World Cup winners medals, my children are everything.

"Mark Johnson set up Borne and I owe Mark everything. I would not have children - I'm convinced of that - if it wasn't for Mark Johnson.

"We can go a long way to buying mums like my wife Caroline an extra week or two, and when Freddie was born at just before 22 weeks, if we could have bought him five more weeks he would be with us now. He would be 11 years old."